JSONP returns no data

Hi
I am trying to retrieve a list of nodes using jsonp. This works fine if I use json directly from a browser.

Would really appreciate any pointers in the right direction.

Here are my request and response headers. The response content is an empty array: []

Request URL:http://www.myhost.com/testrest/node.json?_dc=1331582974127&page=1&start=0&limit=25&callback=Ext.data.JsonP.callback1
    Request Method:GET
Status Code:200 OK
Request Headersview source
Accept:*/*
 Accept-Charset:ISO-8859-1,utf-8;q=0.7,*;q=0.3
 Accept-Encoding:gzip,deflate,sdch
 Accept-Language:en-US,en;q=0.8
 Connection:keep-alive
 Cookie:SESSc5a9244c8264b5631f07d1ded6d64bb2=960m2rgdinhcvdh02tscbgfor0; __utma=34191217.1042080115.1330790487.1330790487.1330790487.1; __utmz=34191217.1330790487.1.1.utmcsr=(direct)|utmccn=(direct)|utmcmd=(none); SESScad999f3b4a94bce60ca03d548931c6a=1PhHl0E0Sr8tp-HBjfmwFIDCNcVj84Pb6EdRc8Xkp9w; has_js=1; Drupal.toolbar.collapsed=0
 Host:www.myhost.com
 Referer:http://www.myclient.com/SampleApp/
 User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_7_3) AppleWebKit/535.11 (KHTML, like Gecko) Chrome/17.0.963.79 Safari/535.11
 Query String Parametersview URL encoded
 _dc:1331582974127
 page:1
 start:0
 limit:25
 callback:Ext.data.JsonP.callback1
 Response Headersview source
 Cache-Control:no-cache, must-revalidate, post-check=0, pre-check=0
 Connection:close
 Content-Length:2
 Content-Type:application/json
 Date:Mon, 12 Mar 2012 20:11:15 GMT
 ETag:"1331583075"
 Expires:Sun, 19 Nov 1978 05:00:00 GMT
 Last-Modified:Mon, 12 Mar 2012 20:11:15 +0000
 Server:Apache/2.2.14 (Ubuntu)
 X-Powered-By:PHP/5.3.2-1ubuntu4.10

My endpoint config is

Server info main object:
stdClass Object
(
    [module] => rest_server
    [endpoint] => testrest
    [endpoint_path] => testrest
    [debug] => 1
    [settings] => Array
        (
            [formatters] => Array
                (
                    [json] => 1
                    [jsonp] => 1
                    [bencode] => 
                    [php] => 
                    [rss] => 
                    [xml] => 
                    [yaml] => 
                )

            [parsers] => Array
                (
                    [application/json] => 1
                    [application/vnd.php.serialized] => 
                    [application/x-www-form-urlencoded] => 
                    [application/x-yaml] => 
                    [multipart/form-data] => 
                )

        )

)